Coal tar or melted conveyor belt possible causes of 'unusual' carcinogenic substance at Pike River
Tuesday, 11 August 2020
Coal tar or a melted conveyor belt are possible causes of an 'unusual' carcinogenic substance found at Pike River, an expert says.
Underground workers recently withdrew from the Pike River Mine after samples from an “unusual substance” on the walls and roof of the tunnel returned positive results for the presence of carcinogens.
Professor David Cliff from the Sustainable Minerals Institute at The University of Queensland in Australia advised New Zealand Police on the possibility of recovery operations at Pike River in 2010 and 2011.
He said the substance was possibly coal tar or melted rubber from the mine’s conveyor belt.
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The 2.3-kilometre Pike River mine drift, or access tunnel, has been entered with the aim of finding out what caused the 2010 explosions and to recover any bodies of the 29 workers killed if they are found in the drift.
Dean Dunbar and Bernie Monk, the fathers of Pike River victims, have been involved in a private investigation with electrical expert Richard Healey into the disaster.
They have previously said data they have uncovered from the mine suggests the second explosion happened in the drift and was caused by the conveyor belt being turned on.
Police discussed turning on the conveyor belt after the first explosion to allow any trapped and injured miners the chance to ride it out. However, in May 2019 a police investigation found no evidence it was turned on.
Cliff said it was possible that rubber could vaporise at high temperatures and stick to surfaces once it cooled and condensed.
He said he had investigated the conveyor belt theory and found no scientific evidence that it was turned on.
He said it was more likely that the carcinogenic substance was coal tar. He had seen coal tar form in a mine drift after an explosion and fire at Australian coal mine North Goonyella.
Coal tar contains polycyclic aromatic hydrocarbons (PAHs) which are cancer-causing when exposed to skin. They are not found in the air unless at very high temperatures.
“It’s very rare but it is distilled out of burning coal. At high temperatures of about 800 degrees Celcius PAHs are vapour, but once they cool down … they would have become solid and stuck to the surfaces,” he said.
The agency could choose to clean the coal tar out of the tunnel, which had been done at North Goonyella, or have the underground staff fully enclosed in hazmat suits.
Either way recovery and evidence gathering operations would be significantly affected, he said.
“They have to be very careful. It will slow them down and as they go further up the drift the more [coal tar] there will be. It could be useful to use robots to assess the top of the drift,” he said.
Pike River Recovery Agency chief operating officer Dinghy Pattinson said the team working underground had recently encountered the “unusual substance” on the walls and roof of the tunnel, and samples taken were positive for the presence of carcinogens.
“As soon as we received notification back from our independent testing facility, we stopped work underground and withdrew the mine workers,” Pattinson said.
“We are now working with mining experts and WorkSafe to understand what the results of the testing mean for our operations.”
Pattinson said the team, made up of experienced underground miners, had noticed the substance 1550 metres up the drift. He said the substance was “a dark coating” on the walls and roof of the mine drift that had not been present up to 1500m. Further testing is expected to reveal what the substance is.
“At this stage we’re working with experts to determine more information about the results.”
All items recovered from the Pike River Mine drift had been handed to the police forensics team on the site.
Police had been notified and immediately ceased their work onsite handling potential exhibits, he said.
“The reason we do all the tests we do and plan for every eventuality is so that we can take action when something like this occurs. The health of all workers on site is always our top priority.”
The agency would now undertake a risk assessment to look at the potential effects on operations and ways to mitigate it.
“We don’t know yet how long it will take to ensure the environment underground is suitable for our workers – it will take as long as it needs to take.”
WorkSafe has been notified.